1. Field of Invention
This invention relates to a chair frame for stackable chairs. More specifically, the present invention is related to a chair frame for a stackable chair which incorporates stacking bars which facilitate the stable stacking of chairs utilizing the frame such that the chairs can be safely stored.
2. Description of the Related Art
Chairs which can be stacked upon one another to facilitate their storage are known in the art. For example, such chairs are disclosed in U.S. Pat. No. 3,316,016. Typically, however, when chairs such as those disclosed in U.S. Pat. No. 3,316,016 are stacked the lower surface of the seat bottom of one chair is supported on the seat cushion of the chair below it. Whereas seat cushions generally will serve to support chairs stacked thereon, the flexibility of the cushion can undermine the stability of the resulting stack of chairs such that relatively few chairs can be safely stacked. Further, the leg members of most stackable chairs are secured to the lower surface of the seat portion, and the lower surface of such chairs can define other irregular surfaces. As a result, it is common for impressions of the legs and/or other irregular features of the lower surface of the seat bottoms to remain in the cushions of the chairs when they are unstacked. These impressions are aesthetically undesirable, and over time damage can result, requiring the replacement of the cushion or replacement of the chair.
In order to avoid damage to the seat cushions one prior art design which is disclosed in U.S. Pat. No. 3,203,731 utilizes a folding back portion which is pivoted down to cover the seat cushion, such that the chair stacked above rests on the rear surface of the back portion of the chair below. Whereas this design avoids the problem of an irregular surface of the upper chair resting upon the seat cushion of the chair below, undesirable pressure is still exerted on the seat cushion, and the folding back portion of the chair makes the chair expensive and complicated to manufacture.
Other prior art designs have attempted avoid damage to the seat cushion by providing stacking bars or supports which extend between the front and back legs of the chair. The stacking bars provide a support which engages the frame of the chair below and supports the upper chair on the frame of the lower chair such that the lower surface of the upper chair is spaced from the upper surface of the seat cushion of the chair below. For example, such designs are disclosed in U.S. Pat. Nos. 4,057,288, 5,762,396, and 6,174,029. The use of stacking bars does serve to avoid damage to the seat cushions of the chairs when they are stacked. However, prior art stacking bars are typically straight chair frame portions which rest upon straight frame portions which boarder the seat cushion of the chair below. Unless the frame of the chair above tightly interlocks with the frame of the chair below, the stacking bars may engage the frame portions of the chair below at various locations alone the length of the frame portions of the chair below, or the stacking bars may slide with respect to the frame portions on which they rest. This can cause a stack of chairs to become unstable, thereby limiting the number of chairs that can safely be stacked. For example, depending upon the configuration of the particular chairs being stacked, positioning the stacking bars too far to the rear on the frame portions of the chair below may cause too much of the weight of the stacked chairs to be shifted to the rear, causing the stack of chairs to fall. Of course, if the legs of the upper chair engage the legs of the chair below this front to rear sliding of the stacking bars with respect to the frame portion of the chair below can be avoided. However, configuring the chair frames such that they closely interlock can make stacking and unstacking the chairs difficult, and engagement of the upper chair frame with the chair frame of the chair below can cause damage to both chairs.